The conservation ecology of Canterbury mudfish (Neochanna burrowsius).

The Canterbury mudfish (Neochanna burrowsius; Galaxiidae) is a small, acutely threatenedfreshwater fish endemic to South Island, New Zealand, which has traits related to its historicoccurrence in the wetlands of the Canterbury Plains. These wetlands have been largelytransformed into productive agricultural land, with consequent fragmentation and localextinction of N burrowsius populations. N. burrowsius now persists primarily in agriculturalwaterways across these increasingly drought-prone plains. I examined aspects of N.burrowsius habitat, inter-specific interactions, and reproduction of importance for theirconservation. Field studies focused on four sites identified as important remnant N.burrowsius habitats. These were distributed across the latitudinal range of N. burrowsius andencompassed different hydrological and agricultural disturbance regimes, and fishcommunities.Distributions of N. burrowsius within each site were patchy. Furthermore, the location of N.burrowsius aggregations within sites was temporally variable, and was influenced by changesin habitat quality and the presence of predatory fish. Predatory fish also affected N.burrowsius activity and abundance. At sites with intermittent flow that regularly dried up,successful strategies of drought survival were dependent on the size of N. burrowsius.Comparisons between populations indicated differences in size structure, individual growth,recruitment, deformities, disease, and parasitic infection. Experimental investigationshighlighted the behavioural and physiological plasticity of N. burrowsius' responses tocompetition, environmental conditions during spawning, and the ability of embryos to toleratehypoxia that likely aid survival in wetland habitats. Macrophytes were also revealed to be akey element in N. burrowsius habitat, with particular macrophyte species associated withdifferent N. burrowsius life stages, and providing spawning substrate critical to the survival ofeggs.This research indicates that hydrological disturbance and the presence of predatory fish likelyhad a greater effect on population characteristics than the presence of competitors,geographical location, and direct agricultural disturbance. Thus, recognising these factorswill be critical in the conservation of N. burrowsius.